Electrophotographic plate comprising a photoconductor dispersed in a resin binder

ABSTRACT

AN ELECTROPHOTOGRAPHIC COPY MATERIAL COMPRISING A SUPPORT AND A LIGHT-SENSITIVE OR PHOTOCONDUCTIVE LAYER FORMED ON ONE SURFACE OF SAID SUPPORT BY A RESINOUS BINDER, WHEREIN SAID PHOTOCONDUCTIVE LAYER CONTAINS A PHOTOCONDUCTIVE SUBSTANCE AND IS FORMED BY A SERIES OF STEPS OF (1) DISPERSING SAID PHOTOCONDUCTIVE SUBSTANCE IN AN AQUEOUS EMULSION PREPARED BY EMULSIFYING A SYNTHETIC FILM-FORMING RESIN OR A NATURAL FILM-FORMING RESIN IN AN AQUEOUS EMULSIFIER SOLUTION CONTAINING A VOLATILE BASIC COMPOUND AND AN ACIDIC COMPOUND THEREAFTER (2) COATING THE RESULTANT EMULSION CONTAINING DESPERSED PHOTOCONDUCTIVE SUBSTANCE ON SAID SUPPORT, AND THEN DRYING THE COATED SUPPORT.

United States Patent 3,704,122 ELECTROPHOTOGRAPHIC PLATE COMPRISING APHOTOCONDUCTOR DISPERSED IN A RESIN BINDER Nario Yamaguchi, SakaeShimizu, and Kazuo Tubuko, Tokyo, Japan, assignors to Kabushiki KaishaRicoh, Tokyo, Japan No Drawing. Continuation of abandoned applicationSer. No. 780,282, Nov. 29, 1968. This application .iune 10, 1971, Ser.No. 151,926 Claims priority, application Japan, Dec. 6, 1967, 42/77,946,42/77,947; Dec. 12, 1967, 42/79,629; Dec. 23, 1967, 42/82,581; Dec. 27,1967, 43/

Int. Cl. G03g 5/04 US. Cl. 961.8 6 Claims ABSTRACT OF THE DISCLOSUREThis application is a continuation of application Ser. No. 780,282,filed Nov. 29, 1968 and now abandoned.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to an electrophotographic copying material comprising a supportand a photoconductive layer formed on one surface of said support by awater-emulsified resinous binder.

Description of the prior art The electrophotographic copying materialsin the prior art were manufactured by a method wherein a metallic plate,or a special paper whose back had been processed to render itelectroconductive, was used as a support. A light-sensitive orphotoconductive layer-forming solution obtained by dispersing aphotoconductive substance in a binder solution, prepared by dissolving aresin in an organic solvent, was applied onto the surface of saidsupport and then dried. In this prior method, however, a water solubleresin was not generally used for said purpose because it does notprovide the photoconductive layer formed on the support with thecritical electrostatic characteristics-especially, high electricresistance required for photoconductive layers. Accordingly, it wasformerly considered particularly advisable to use a natural or syntheticresin which was soluble only in an organic solvent, and also which wouldnot interfere with the electrostatic characteristics of thephotoconductive layer formed on the support. However, in those cases inwhich a resin that is soluble only in an organic solvent was employedfor said purpose, it was necessary to pre pare the binder by dispersingthe resin in a large quantity of organic solvent because of the generalrequirement for using a homogeneous dispersion of the photoconductivesubstance in said binder. As a result, there were various drawbacks inthe manufacture of electroice photographic copying materials in theprior art, such as:

(a) It was conventional to employ expensive organic solvents so that itwas necessary to recover these solvents during the manufacturingprocess.

(b) Most of the organic solvents used are inflammable and involve therisk of explosion, so that preventive measures were required therefor.

(c) Many organic solvents used are hazardous to health, so thatprotective measures against their effects were also required.

(d) Expensive special measures and coating devices were required to forma photoconductive layer on the support.

(e) Because an air-knife is inoperable as a coatingapplying means forsuch prior compositions, high-speed coating was impractical.

In view of the fact that the above-mentioned disadvantages may beeliminated, if the resin used for the binder is water-emulsive orwater-dispersive, there have been proposed a variety of water-emulsiveor waterdispersive resins. However, the prior copying materialsheretofore produced from these materials had such drawbacks as poorelectrostatic characteristics. For example, when an electrostatic chargewas impressed on the photoconductive layer by corona discharge, thecharged potential become low. Also, the decay of the electric potential,i.e. the dark-decay when said materials were left in a dark place afterbeing charged, was great. Accordingly, such materials have proven to bequite unsatisfactory for practical use.

SUMMARY OF THE INVENTION It is, therefore, an object of the invention toprovide an electrophotographic copying material which avoids theaforesaid drawbacks of electrophotographic copying materials made withthe water-emulsified resinous binders in thet prior art.

Another object of the invention is to provide a wateremulsified resinousbinder which is suitable for forming a photoconductive layer havingsuperior electrostatic characteristics in an electrophotographic copyingmaterial.

It is another object of the invention to provide an electrophotographiccopying material which can be produced economically while avoiding thehazards that art encountered in the process of manufacturing said copying material in the prior art.

In brief, the electrophotographic copying material of the presentinvention is obtained by the following process: a resinous binder havingfilm-forming properties is emulsified with an aqueous emulsifiersolution which comprises (1) at least one volatile basic compoundselected from the group consisting of nitrogen-containing compounds and(2) at least one acidic compound selected from the group consisting of(a) a natural resin having an electric resistance of at least 10 t'Z-cm.and containing a resin acid, (b) a synthetic resin having an electricresistance of at least 10 Q-cm. and an acid value, i.e. acid reaction,(c) an alicyclic compound having a carboxyl radical, (d) an aliphaticcarboxylic acid, (e) an aromatic carboxylic acid, and (f) acidanhydrides of said carboxylic acids. The emulsion thus obtained hasdispersed therein the photoconductive substance. The surface of asupport is coated with said dispersion and dried thereafter. Also, inthe present invention, there are employed for the aforesaid resinousbinder a variety of natural resins as well as synthetic resins havingfilmforming properties. The emulsion of the resin is produced by usingthe minimum quantity of organic solvent. Furthermore, the emulsionproduced in such a way is characterized by being comprised of theresinous binder in the form of dispersed fine grains having a diameterof a few ,u, so that the resultant photoconductive layer is highlyhomogeneous.

In the present invention, the water-emulsified resinous binder used toform a photoconductive layer is one member selected from the groupconsisting of the following members (a)-(f).

(a) An emulsion produced by emulsifying a film-forming resinous binderwith an aqueous solution of a natural resin containing a resin acid andhaving an electric resistance of at least SZ-cm. and containing avolatile basic compound therein.

(b) An emulsion produced by emulsifying a film-forming resinous binderwith an aqueous solution of an alicyclic compound having carboxylradical and containing a volatile basic compound therein.

(c) An emulsion produced by emulsifying a film-forming resinous binderwith an aqueous solution of at least one acid selected from the organicacid group consisting of an aliphatic carboxylic acid, an aromaticcarboxylic acid, and an acid anhydride of said carboxylic acids andcontaining a volatile basic compound.

(d) An emulsion produced by emulsifying a film-forming resinous binderwith an aqueous solution of a synthetic resin having an acid value andan electric resistance of at least 10 n-cm. and containing a volatilebasic compound therein.

(e) An emulsion produced by using an organic solution of a syntheticresin such as employed for (d) to supply the film-forming resinousbinder and emulsifying the organic solvent solution with an aqueoussolution containing a volatile basic compound. In the case of thisparticular emulsion, the combined use of a small amount of a heavy metalsalt of a naphthenic acid as the binder set ting agent is preferable.

(f) An emulsion produced by employing, as a filmforming resinous binder,a copolymer selected from the group consisting of a vinyl copolymerhaving an epoxy radical (O), and a vinyl copolymer having a hydroxylradical (OH) in its molecular end, and by emulsifying said binder withan aqueous solution of a volatile basic compound and an acid compoundsuch as are applied in (a)-(b).

' It is to be noted that, although it is possible to dissolve a resinousbinder in an organic solvent and then to emulsify the resultant solutionin water by means of an ordinary anionic or noniouic surface activeagent, the photoconductive layer formed by employing an emulsion soobtained has too low an electric resistance to provide a sufficientelectrostatic light-sensitivity and, therefore, is not of practical use.

As can be seen in the foregoing, in the binders to be applied in thepresent invention, an aqueous solution of a volatile basic compound is aprincipal component of the emulsion of the resinous binder. To be morespecific, these binders are emulsified by an emulsifier produced by thecombination of said volatile basic compound and an acidic compound (suchas a natural resin containing a resin acid in the case of (a), acarboxylic acid of an alicyclic compound in the case of (b), an organicacid group in the case of (c), and a synthetic resin having an acidvalue in the case of (d) as described in the foregoing).

Next, as said volatile basic compound to be employed in the emulsion inthe present invention, nitrogen containing compounds, such as ammonia,methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine,triethylamine, propylamine, butylamine, hexylamine, ethylenediamine,arylamine, morpholine, piperidine and hydrazine, are suitable. However,the applicable compounds for said purpose covers also a wide range ofamine compounds, which are volatile and water-soluble, such as aliphaticprimary amines, secondary amines, and tertiary amines. Besides, inemulsifying resinous binders such as natural resins and synthetic resinswhich have film-forming properties, said volatile basic compounds areemployed in the form of an aqueous solution.

As the acid compound, i.e. a natural resin containing a resin acid, tobe employed for the aforesaid (a), a resin having an electric resistanceof at least 10 n-cm. is selected lest its special quality should bedeteriorated when applied in a photoconductive layer. Natural resinshaving such a property and considered suitable for use include, forexample, elemi, Gurjun balsam, jalap, scammonia, amber, bdellium,sagapenum, Euphorbium, myrrh, Opopanax, various kinds of dammar (such asBenak, dead dammar, Melanty, Chan, yon banoun, papuan dammar), shellac,acaroid, dragon brad, mustic, styrax, Canada balsam, Mecca balsam,copai-ba balsam, Peru balsam, guaiac, tacamahac, galvanum, gamboge,olibanum, ammoniac, asafetida, various kinds of copal (such as kauricopal, soft manila copal, hard manila copal, congo copal, benguelacopal, angora copal, Madagascar copal, Zanzibar copal, demera copal,hard bornea copal, New Zealand kauri copal), various kinds of rosin(such as gum rosin, heterogeneous rosin, polymerized rosin, hydrogenatedrosin, tall oil, rosin maleate, rosin oxide, hardened rosin, ester gum),benzoic acid, sandarack, true balsam, and kawakawa resin. Included arevarious products whose principal component is one of those enumeratedabove, which have been put on the market under different trade names.

Acid compounds for (b), i.e. carboxylic acids of alicyclic compounds,include, for example, abietic acid, bisnorcholanic acid, fi-boswelicacid, chenodesoxylcholic acid, chenobic acid, cholanic acid, cholicacid, dehydrocholic acid, dioxylcoal acid, doisynolic acid,erythrophleinic acid, etiocholanic acid, glycocholic acid, glychyrrhizicacid, oleanolic acid, helvolic acid, hiodesoxycholic acid, isocholicacid, naphthenic acid, norcholanic acid, e-pimaric acid, quillaic acid,ursodesoxycholic acid, and ursolic acid.

Acid compounds for (c), i.e. an aliphatic carboxylic acid, an aromaticcarboxylic acid, and an acid anhydride of said carboxylic acids, includemany applicable acids, and examples are enumerated as follows:

Aliphatic saturated monocarboxylic acid: caproic acid, heptanoic acid,caprylic acid, pelargonic acid, capric acid, n-undecylenic acid, lauricacid, n-tridecylenic acid, myristic acid, n-pentadecylenic acid,palmitic acid, margaric acid, stearic acid, n-nonadecylenic acid,arachidic acid, n-heneicosanoic acid, behenic acid, n-tricosanoic acid,lignoceric acid, n-pentacosanoic acid, ceratic acid, n-heptacosanoicacid, montanic acid, n-nonacosanoic acid, melissic acid,n-hentriacontanoic acid, n-dotriacontanoic acid, n-tetratriacontanoicacid, ceroplastic acid, n-hexatriacontanoic acid, n-octatriacontanoicacid and n-hexatetracontanoic acid.

Aliphatic olefin monocarboxylic acid: 2-hexenoic acid, 3-hexenoic acid,4hexenoic acid, S-hexenoic acid, 2- methyl-2-pentenoic acid,3-methyl-2-pentenoic acid, 4- methyl-Z-pentenoic acid, 4-methylpentenoicacid, u-ethylcrotonic acid, 2,2-dimethyl-3-butenoic acid, 2-heptenoicacid, 2-octenoic acid, 4-decenoic acid, 9-decenoic acid, 9- undecenoicacid, IO-undecenoic acid, 4-dodecenoic acid, S-dodecenoic acid,4-tetradecenoic acid, 9-tetradecenoic acid, 9-hexadecenoic acid,2-octadecenoic acid, cis-6-octadecenoic acid, 9-octadecenoic acid, oilacid, elaidic acid, ll-octadecenoic acid, ll-octadecenoic acid,9-eicosenoic acid, ll-eicosenoic acid, ll-docosenoic acid, l3-docosenoicacid, erucic acid, IS-tetracosenoic acid and mycolipenic acid.

Aliphatic diolefin carboxylic acid: 2,4-hexadienoic acid, diallylaceticacid, geranium acid and 2,4decadienoic acid.

Aliphatic higher unsaturated monocarboxylic acid: hexadecatrienoic acid,linoleic acid, linolenic acid, 6,9,12- octadecatrienoic acid,eicosadienoic acid, eicosatrienoic acid, decosadienoic acid,decosatrienoic acid and heracodienoic acid.

Aliphatic saturated dicarboxylic acid: adipic acid, pimelic acid,suberic acid, azelaic acid, sebacic acid, undecane dicarboxylic acid,dodecane dicarboxylic acid, brassylic acid and tetradecane dicarboxylicacid.

Aromatic monocarbobylic acid: benzoic acid, toluylic acid, m-toluylicacid, p-toluylic acid, dimethylbenzoic acid, o-ethylbenzoic acid,m-ethylbenzoic acid, pethylbenzoic acid, 2,3,4-trimethylbenzoic acid,2,3,5-trimethylbenzoic acid, 2,3,6-trimethylbenzoic acid,2,4,5-trimethylbenzoic acid, 2,4,6-trimethylbenzoic acid,3,4,5-trimethylbenzoic acid, cuminic acid, cinnamic acid, o-nitrobenzoicacid, m-nitrobenzoic acid, p-nitrobenzoic acid, 2,4-dim'trobenzoic acid,3,5-dinitrobenzoic acid, o-chlorobenzoic acid, p-chlorobenzoic acid,o-fluorobenzoic acid, m-fluorobenzoic acid, p-fluorobenzoic acid,o-bromobenzoic acid, m-bromobenzoic acid, p-bromobenzoic acid, 0-iodobenzoic acid, m-iodobenzoic acid, p-iodobenzoic acid,2,3-dichlorobenzoic acid, 2,5-dichlorobenzoic acid, 2,6- dichlorobenzoicacid, 3,4-dichlorobenzoic acid, 3,5-dichlorobenzoic acid,2,3-dibromobenzoic acid, 2,4-dibromobenzoic acid, 2,5-dibromobenzoicacid, 2,6-dibromobenzoic acid, 3,4-dibromobenzoic acid,3,5-di'bromobenzoic acid, 2,3-diiodobenzoic acid, 2,4-diiodobenzoicacid, 2,5- diiodobenzoic acid, 2,6-diiodobenzoic acid, 3,4-diiodobenzoicacid, 3,5-diiodobenzoic acid, 2-ch1oro-5-nitrobenzoic acid,3-chloro-6-nitrobenzoic acid, 2-bromo-5- nitrobenzoic acid,Z-chIoro-cinnamic acid, 2-cyanocinnamic acid, 2-naphthoic acid,5-chloronaphthoic acid, 18- naphthoic acid and 5-bromonaphthoic acid.

Aromatic dicarboylic acid: phthalic acid, isophthalic acid, terephthalicacid, S-chlorophthalic acid, 4-chlorophthalic acid, 3,6-dichlorophthalicacid, tetrachlorophthalic acid, tetrabromophthalic acid,tetraiodophthalic acid, naphthalic acid, naphthalene-l,2-dicarboxylicacid, naphthalene-1,4-dicarboxylic acid and naphthalene-1,5- dicrboxylicacid.

Aromatic tricarboxylic acid: 1,2,3-hemimellitic acid and1,2,4-trimellitic acid.

As synthetic resins having an acid value, which can be employed for (d)and (e), a synthetic resin having an electric resistance of at leastQ-cm. is selected for the same reasons as in the case of (a) above.Therefore, the suitable synthetic resins include, for example, copolymerresins of acrylic ester, acrylic-alkyd resin, pure alkyd resin, epoxyester resin, non-drying type pure alkyd resin, rosin-modified alkydresin, phenol-modified alkyd resin, styrenated alkyd resin, naturalresin-modified phenolic resin, natural resin-modified maleic acid resin,natural resin-modified pentaerythritol resin, natural resin-modifiedfumaric acid resin, and so forth.

In the present invention, in the case of the emulsification of aresinous binder comprising a natural resin or a synthetic resin havingfilm-forming properties as stated below, one or two kinds of acidiccompounds having the aforesaid emulsifier component are employed. Forthe combination of said acidic compound with a volatile basic compound,a mixing ratio of 1 mol of at least one kind of acidic compound to 1-2mols of at least one kind of basic compound, will effect homogeneousemulsification of a resinous binder in water.

As the resinous binder, although a variety of resins having film-formingproperties are applicable, such resins as enumerated hereunder are mostsuitable for the aforesaid (a)(d) in the present invention.

(A) Natural resin and natural resin-modified resin: colophony (rosin),modified colophony, dammar resin, ethyl cellulose acetate, hydroxyethylcellulose acetate, cellulose acetostearate, and ethylcellulose stearate(B) vinyl polymer and substituted vinyl polymer:

(I) Photoconductive vinyl polymer: poly-N-vinylcarbazole,N-vinylcarbazole-ethylacrylate copolymer (II) Polyvinyl ester:vinylacetate resin, vinylacetatecrotonic acid copolymer,vinylacetate-vinylstearate copolymer, polyvinylstearate,vinylacetate-maleic acid copolymer (III) Vinylchloride polymer orvinylchloride copolymer: polyvinylchloride, vinylchloride-vinylisobutylether copolymer, vinylchloride vinylacetate-vinylalcohol copolymer,vinylchloride-vinylacetate-maleic anhydride copolymer,polyalkylmethacrylate (IV) Polyvinyl acetal and vinylacetal copolymer:polyvinyl butyral, vinyl butyral-vinylacetate copolymer (V) Polystyreneor styrene copolymer: polystyrene, styrene-methacrylic acid copolymer,styrene-butadiene copolymer, styrene-dimethylitaconate copolymer (VI)Polymer of methacrylic ester: polymethacrylic ester,polyalkylmethacrylate, polymethylmethacrylate (C) Condensated polymer:styrenated alkyd resin, alkyd-modified rosin resin, alkyd-modifiedphenol resin, epoxy ester resin, pentaerythritol phthalate resin,polycarbonate (D) Other resins and synthetic gums: poly indene, polycyclopentadiene, silicone resin, ketone resin, rubber chloride Theresinous binder to be employed for the aforesaid (f) in the presentinvention includes vinyl copolymer resins obtained by copolymerizing atleast one member selected from the vinyl monomer group consisting of,for example, glycidyl acrylate, glycidyl methacrylate, hydroxyethylmethacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, 5- hydroxypentylvinyl ether (CH =CHOCH CH CH CH CH OH)with at least one member selected from the monomer group consisting of,for example, styrene, acrylate, methacrylate, acrylonitrile, vinylchloride, vinylidene chloride, vinyl acetate, acrylic acid, methacrylicacid, crotonic acid, itaconic acid, maleic acid, and fumaric acid.

The materials of the water-emulsified resinous binder to be employed inthe present invention are as enumerated above. The materials other thansaid water-emulsified binder to be employed in forming a photoconductivelayer can be any support, photoconductive substance, and

sensitizer as conventionally used. As the photoconductive substance, forinstance, zinc oxide, titanium oxide, cadmium sulfide, zinc selenide,and so forth may 'be cited, and above all, zinc oxide and titanium oxideare desirable. As for the sensitizer to be employed, Phthalein dyes suchas Fluorescein, Eosin, Erythrosine, and Rose Bengal, Triphenylmethanedyes such as Malachite Green, Crystal Violet, Basic Fuchsin, MethylGreen, Brilliant Green, Bromophenol Blue, and Tetrabromophenol Blue,Cyanine dyes such as Cryptocyanine and Pinacyanol, Heterocyclic dyessuch as Acridine Orange, mixed dyes such as Methylene Grey, andfurthermore, Alizarine Red S. Alizarine, and Quinizarin may be cited. Asfor the support, not only a metallic plate but also either paper or asheet film whose back has been processed for electric conductivity canbe employed, but it is desirable that the surface electroresistivityresulting from said process for electric conductivity be less than 10Q-cm. and it is further advisable for it to be less than 10' Q-crn.

A desirable impregnation of the aforesaid sensitizer in aphotoconductive layer can be attained by mixing the sensitizer withinthe range of 0.01-5.0% per total weight of zinc oxide, for example, tobe contained in the photoconductive layer.

The copying material of the present invention is produced by the stepscomprising: one member selected from the group consisting of emulsionmembers (a)-(f) as described above is dispersed with a photoconductivesubstance; the emulsion wherein said photoconductive substance isdispersed is applied as a coating to the surface of a support, by suchmethods as the centrifugal coating method, spray coating method andbrush coating method. The surface thus coated with said emulsion isdried thereafter. It is noted, in this respect, that according to thepresent invention, in the manufacturing process of theelectrophotographic copying material, the coated surface of the support,that is to say, the photoconductive layer, is impregnated with avolatile basic compound, so that it is necessary to provide a sufiicienttemperature for volatilization of said basic compound to expedite thedrying of the layer. Therefore, it is desirable to take such measures asa. hot-air drying method or infrared ray drying method for the sake ofrapid drying. As for the drying temperature, though it may depend on thekind of the volatile basic compound employed, the most desirable dryingtemperature is not lower than 100 C. and also comes within the range ofsuch temperatures as will not cause the resin contained in thephotoconductive layer to deteriorate and thereby interfere with itscharacter. The maximum temperature is ordinarily 250 C.

There will be no inconvenience even if there remains a volatile basiccompound, in the formed photoconduc- V tive layer, in an amount notexceeding 0.5% per total weight of the solid matter (i.e. saidphotoconductive layer).

Among the electrophotographic copying materials, the copying materialhaving a photoconductive layer formed by the aforesaid (f) member isespecially endowed with an excellent character. In other words, an epoxyradical or hydroxyl radical contained in a resinous binder shows abridge-formation reaction in the drying process for formation of aphotoconductive layer and thereby forms a network structure, so that thelayer thus formed has outstanding weather-proofness. For instance, evenwhen it is used for copying purposes in an atmosphere of high humidity,the copied picture as well as the characteristic obtained thereby is byno means inferior to those obtained in an atmosphere of normal humidity.This is attributable to the fact that a network structure formed by theresinous binder in the photoconductive layer impedes the adsorption ofmoisture from the atmosphere by the photoconductive substance. It isfurther noted that, in the aforesaid drying process, a bridge-formationreaction is readily expedited by the existence of a dibasic acid, atertiary ammonium salt, and a quaternary ammonium salt in case of anepoxy radical; while in case of a hydroxyl radical at the end of along-chain molecule it is expedited by the presence of a polybasic acidof an amino resin, and the like. Accordingly, a binder which has such aradical, an acid and a salt cause a bridge-formation reaction at thetime of forming a photoconductive layer on the surface of a support asseen above.

DETAILED DESCRIPTION OF THE INVENTION Example 1 3 gms. of StabeliteResin (trade name of a product of Hercules Co. of U.S., havinghydrogenated rosin as its principal component and containing abieticacid as a resin acid) is added to 70 gms. of a xylene solution of 70%silicone resin (manufactured by Shinetsu Kagaku Kogyo Kabushiki Kaishain Japan, and named Silicone Resin KR-211), and then the mixture thusobtained is heated at 70 C. The substance thus treated is emulsified byadding steadily a solution obtained by dissolving 3 gms. oftriethylamine in 100 gms. of water, while being agitated by a homomixer.

Meanwhile, another solution is prepared by adding 100 gms. ofphotoconductive zinc oxide to 100 gms. of water and then dispersing sameby a homomixer, and this solution is blended with 80 gms. of theaforesaid emulsion and then agitated. Next, the solution thus processedis further blended with 5 cc. of a methanol solution comprisingBromophenol Blue 1%, Fluorescein 0.5 and Rose Bengal 0.1%, and agitated.

The photoconductive layer forming solution thus obtained is applied tocoat the surface of an art paper, whose back has been processed forelectric conductivity, to such 8 an extent that the weight after thedrying process will be 25 gms./m and thereafter is dried by theinfrared-ray drying method.

A picture, which is obtained by employing such an electrophotographiccopying paper impressed with electric charge by an ordinary method andthrough either wet-process development or dry-process developmentsubsequent to its exposure, is superb in the light of the fact that nosuch picture has ever been obtained using a copying paper produced byforming a photoconductive layer by the employment of a resinous binderemulsified with an ordinary surface active agent.

Example 2 When 100 gms. of Styrezol 4440 (50%-mineral turpentinesolution of styrenated alkyd resin, manufactured by Dai Nippon Ink andChemical Inc.) was employed in lieu of KR-Zl l, which was employed inExample 1 above, while otherwise following the processes as that inExample 1 for preparing an electrophotographic copying paper andproducing a picture by an ordinary electrophotographic means, theresulting picture was superb.

Example 3 3 gms. of Dammar Gum (manufactured by Arakawa Rinsan KagakuKogyo Kabushiki Kaisha, and having dammarol acid as a resin acidcomponent) is added as in Example 1 and the mixture is heated up to atemperature within the range of -80 C. to effect dissolution thereof.The solution thus obtained is agitated by a homomixer, while anothersolution prepared by dissolving 3 gms. of ethylamine in 100 gms. ofwater is added steadily, and is thereby emulsified.

gms. of the resultant emulsion is added to the zinc oxide dispersedsolution, as prepared in the above Example 1, and is agitated. Asensitizing dye solution is also added in the same way as in Example 1in producing the photoconductive layer forming solution.

The employment of the aforesaid processes in producing a picture in thesame way as in Example 1 has resulted in a superb picture.

Example 4 In this case, 4 gms. of Ester Gum (Product of Hercules Co. inU.S., having abietic acid as a resin acid component) is added to gms. ofStyrezol 4440, and the mixture is heated up to a temperature within therange of 7080 C. to elfect dissolution thereof. The solution thusobtained is agitated by a homomixer, while another solution prepared bydissolving 4 gms. of triethylamine in 100 gms. of water is addedsteadily, and is thereby emulsified. 80 gms. of the resultant emulsionis added to the zinc oxide dispersed solution, as prepared in Example 1,and agitated. A sensitizing dye solution is also added in the same wayas in Example 1 in producing a photoconductive layer forming solution.

When an electrophotographic copying paper, which had been prepared inthe same way as in Example 1, was employed in producing a picture by anordinary process, the resultant picture was superb in quality.

Example 5 In this case, 2 gms. of Shellac (product of Japan ShellacIndustrial Co., Ltd., containing aleuritic acid as its principalcomponent) is added to 80 gms. of Beckozole 1341 (a 60%-Xylene Naphthasolution of phenolized alkyd resin, manufactured by Dai Nippon Ink andChemicals Inc.), and the mixture thus obtained is heated up to atemperature within the range of 70-80 C. to effect dissolution thereof.The solution thus obtained is agitated by a homomixer, while anothersolution prepared by dissolving 8 gms. of 28% aqueous ammonia in 100gms. of water is added steadily, and is thereby emulsified. On the otherhand, another solution is prepared by adding 100 gms. of photoconductivezinc oxide into 100 gms. of water and then dispersing same by ahomomixer, and thereafter 90 gms. of the aforesaid emulsion is added tothis dispersed solution and agitated. The mixture thus obtained isfurther blended with 6 cc. of a methanol solution containing 2% RoseBengal.

The photoconductive layer forming solution thus obtained is applied tothe surface of a baryta paper, Whose back has been processed forelectric conductivity, to such an extent that the weight subsequent tothe drying process will be 35 gms./m2, and thereafter is dried.

An electrophotographic copying paper obtained as above is impressed withan electric charge by an ordinary method, and can be developed and fixedby dry-process development subsequent to exposure. This materialproduces a superb photographic effect, so that the picture obtainedthereby may be used as a master for offset printing after making ithydrophilic.

Example 6 In this case, 3 gms. of Polymer Rosin (product of Hercules Co.in US, having abietic acid as a resin acid component) is added to 100gms. of Beckozole P-787 (a 45%-xylene solution of epoxide ester,manufactured by Dai Nippon Ink and Chemicals Inc.), and the mixture isheated up to a temperature within the range of 7080 C. to effectdissolution thereof. The solution thus obtained is agitated by ahomomixer, While another solution prepared by dissolving 3 gms. ofmorpholine in 100 gms. of water is added steadily, and is therebyemulsified.

Next, 100 gms. of the resultant emulsion is added into the zinc oxidedispersed solution, as prepared in Example 1 above, and is agitated. Asensitizing dye solution is also added in the same way as in Example 1.

The photoconductive layer forming solution thus obtained is applied forcoating the surface of an art paper, whose back has been processed forconductivity, to such an extent that the weight after the drying processwill be 25 gms./m3, and is dried thereafter.

This copying material, when used for producing a picture thereon by anordinary electrophotographic process, has brought about a superb effect.

Example 7 In this case, 3 gms. of naphthenic acid is added to 100 gms.of Styrezol 4440, and the mixture is agitated by a homomixer, While asolution prepared by dissolving 3 gms. of morpholine in 100 gms. ofwater is added steadily, and is thereby emulsified. (The emulsion thusobtained is hereinafter referred to as the A solution.)

On the other hand, 100 gms. of photoconductive zinc oxide is added to100 gms. of water and dispersed by a homomixer. The dispersed solutionthus obtained is blended with cc. of a methanol solution comprisingBromophenol Blue 1%, Fluorescein 0.5%, and Rose Bengal 0.1%, and isagitated. (The solution thus obtained is hereinafter referred to as theB solution.)

The aforesaid B solution is blended with 80 gms. of the A solution andthen is agitated. The conductive layer forming solution obtained by theabove process is applied for coating the surface of an art paper, whoseback has been processed for electric conductivity, to such an extentthat the Weight after the drying process will be 25 gms./ m. and isdried thereafter.

The resultant electrophotographic copying material, when impressed withan electric charge by a conventional method and developed by thewet-process or the dryprocess, produced a superb picture in contrast tothe fact that no such a picture has even been obtained by the employmentof an emulsion produced by any conventional surface active agent.

Example 8 In this case, 1 gr. of abietic acid is added to 70 gms. ofKR-211 to be dissolved therein. The solution thus obtained is agitatedby a homomixer, while another solu- 10 tion prepared by dissolving 2gms. of triethylamine in 100 gms. of water is added thereto steadily,and is thereby emulsified.

gms. of the resultant emulsion is then blended with the B solutionreferred to in the foregoing Example 7, and is agitated. By theemployment of the photoconductive layer forming solution thus obtained,an electrophotographic copying paper is produced in the same way as inExample 7. The electrophotographic copying paper thus produced, whenemployed for producing a picture through a conventionalelectrophotographic process, has brought about a superb result.

Example 9 In this case, except for the employment of 28 gms. ofetiocholanic acid in lieu of abietic acid employed in Example 2, thesame steps are applied in producing an electrophotographic copyingpaper. As for the photographic efficiency of the resultant copyingpaper, the same effect as in Example 1 is attained through the sameconventional processes.

Example 10 'In this case, 3 gms. of oleanolic acid is added to 80 gms.of Beckozole 1341 (a 60% xylene naphtha solution of phenol-modifiedalkyd resin, manufactured by Dai Nippon Ink and Chemicals Inc.) anddissolved therein. The solution thus obtained is agitated by ahomomixer, while another solution prepared by dissolving 3 gms. ofmorpholine in 100 gms. of water is added steadily, and is therebyemulsified.

gms. of the resultant emulsion is then blended with the B solutionreferred to in the aforesaid Example 7, and is agitated. By theemployment of the photoconductive layer forming solution thus obtained,an electrophotographic copying paper is produced in the same way as inExample 7. The electrophotographic copying material thus produced, whenemployed for producing a picture through a conventionalelectrophotographic process, has brought about a superb result.

Example 11 In this case, 3 gms. of napthenic acid is added to 110 gms.of Beckozole P-787. The mixture thus obtained is agitated by ahomomixer, while another solution pre pared by dissolving 3 gms. oftriethylamine in gms. of water is added steadily, and is therebyemulsified. On the other hand, 100 gms. of photoconductive zinc oxide isadded to 100 gms. of water and dispersed by a homomixer. The dispersedsolution thus obtained is mixed with 100 gms. of the aforesaid emulsionand is agitated. Next, 6 cc. of methanol solution containing 2% of RoseBengal is added, and this mixture is further agitated. Thephotoconductive layer forming solution thus produced is applied forcoating the surface of a baryta paper, whose back has been processed forconductivity, to such an extent that its weight after the drying processwill be 35 gms./m and is dried thereafter.

The resultant electrophotographic copying material is impressed with anelectric charge by a conventional method, and can be developed and fixedby the dry-process subsequent to exposure. This material produces asuperb photographic image, so that a picture obtained thereby can beused as a master for an offset printing after making it hydrophilic.

Example 12 In this case, 2 gms. of lauric acid was added to gms. ofBeckozole P-787. The mixture thus obtained was agitated by a homomixerwhile another solution, which had been prepared by dissolving 3 gms. oftriethylamine in 100 gms. of water, is added steadily, and thereby abinder solution comprising an emulsion of said resin was produced. 110gms. of the thus produced binder solution was then added to a sensitizersolution comprising 100 gms. of photoconductive zinc oxide, 100 gms. ofwater, and 5 cc. of a sensitizer solution (a methanol solutionconsisting of 1% of Bromophenol Blue, 0.5% of Fluorescein, and 0.1% RoseBengal) and agitated, thereby producing a photoconductive-layer formingsolution. The dispersed solution thus prepared was applied for coatingthe surface of a supportin the present case, an art paper-whose back hadbeen processed for conductivity, to such an extent that the remainder ofthe applied solution on said surface subsequent to the drying processwill be 25 gms./ m. Upon drying said coated support at 130 C. for 1min., an electrophotographic copying material was obtained.

On the other hand, for the purpose of comparison, another bindersolution having the same composition as that of the aforesaid bindersolution, except for substitution of 3 gms. of a surface active agent(such as Nissan Rapizole (dialkylsulfosuccinate manufactured by NihonYushi Kabushiki Kaisha)) for the lauric acid and triethylamine, wasprepared and the same sensitizer solution as in the present inventiondescribed in the foregoing was added thereto, and the thus blendedsolution was further processed in the same way as in the presentinvention, thereby producing a copying material to serve for saidcomparison.

When both of those copying materials which were obtained through theaforesaid processes were impressed with an electric charge by coronadischarge, the material produced by the present invention showed anelectric charge as high as 400 volts, while the other prepared forcomparison could be charged with only 50 volts. Moreover, when each ofsaid copying materials was exposed in accordance with an original copyand developed by the wetprocess, the material produced by the presentinvention formed a clear image of the original copy with high fidelity,while the other prepared for comparison could hardly form any image.

Example 13 In this case, except for the substitution of palmitic acidfor the lauric acid employed for emulsification in the foregoing Example12, the same components and processes as in case of Example 12 wereapplied in obtaining an electrophotographic copying material. Theefiiciency and performance of the thus obtained copying material wereequivalent to that of Example 12.

Example 14 In this case, 3 gms. of stearic acid was added to 100 gms. ofStyrezol 4440. The mixture thus obtained was agitated by a homomixerwhile another solution, which had been prepared by adding v3 gms. ofmorpholine to 100 gms. of water, was added steadily, and thereby abinder solution comprising an emulsion of said resin was produced. 100gms. of the thus produced binder solution was then added to a sensitizersolution having the same composition as that of Example 12, and the thusblended solution was thereafer processed in the same way as in Example12, thereby producing an electrophotographic copying material. Theefficiency and performance of the thus obtained copying material wereequivalent to that of Example 12 of the present invention.

Example 15 In this case, 3 gms. of oleic acid was added to 70 gms. ofSilicone Resin KR-211. The mixture thus obtained was agitated by ahomomixer while another solution, which had been prepared by dissolving3 gms. of triethylamine in 100 gms. of water, is added steadily, andthereby a binder solution comprising an emulsion of said resin wasproduced. 80 gms. of the thus produced binder solution was then added toa sensitizer solution having the same composition as that of Example 12,and the thus blended solution was thereafter processed in the same wayas in Example 12, thereby producing an electrophotographic copyingmaterial. The efficiency and performance of the thus obtained sensitivematerial proved to be equivalent to that of Example 12 of the presentinvention.

Example 16 In this case, 3 gms. of ricinoleic acid was added to gms. ofBeckozole 1341. The mixture thus obtained was agitated by a homomixerwhile another solution, which had been prepared by blending 10 gms. of28%-ammonia water with 100 gms. of water, was added steadily, andthereby a binder solution comprising an emulsion of said resin wasproduced. gms. of the thus produced binder solution was then added to asensitizer solution having the same composition as that of Example 12,and the resultant solution was processed in the same Way as in Example12, thereby producing an electrophotographic copying material. Thecopying material thus produced proved to be equivalent to that ofExample 12 in its efficiency as well as performance.

Example 17 In this case, there were prepared several binders:

A binder, which was obtained by emulsifying the same silicone resin aswas employed in Example 15 by means of an emulsifier produced bycombining phthalic anhydride with triethylamine,

A binder, which was obtained by emulsifying the same styrenated alkydresin as was employed in Example 14 by means of an emulsifier producedthrough combination of cobalt naphthenate (a hardener), p-chlorobenzoicacid, and trirnethylamine,

A binder, which was obtained by emulsifying the aforesaid silicone resinby means of an emulsifier produced by combining naphthalic acid withtriethylamine,

A binder, which was obtained by emulsifying the aforesaid silicone resinby means of an emulsifier produced by combining tetrachlorophthalic acidwith triethylamine, and

A binder, which was obtained by emulsifying the aforesaid styrenatedalkyd resin by an emulsifier produced by combining tetrachlorophthalicacid with trimethylamine.

By the employment of each of the binders enumerated above, and byapplying the method of treatment similar to that employed in Example 12,electrophotographic copying materials were produced respectively. Eachof the resultant copying materials proved to be equivalent to that ofExample 12 in its efliciency and performance.

Example 18 In this case, 10 gms. of Styrezol J-718 (a 50%-high solvencymineral turpentine solution of styrenated alkyd resin, whose acid valueis approximately 10, manufactured by Dai Nippon Ink and Chemicals Inc.)was added to gms. of Styrezol 4440, and the mixture thus obtained wasagitated by a homomixer while another solution, which had been preparedby dissolving 3 gms. of triethylamine in 100 gms. of water, was addedsteadily, and thereby a binder solution comprising an emulsion of theaforesaid Styrezol 4440 resin was produced. On the other hand, 100 gms.of photoconductive zinc oxide was added to 100 gms. of water, andfurthermore, while this mixture was agitated by a homomixer, 5 cc. of asensitizing dye solution (a methanol solution comprising 1% ofBro'mophenol Blue, 0.5% of Fluorescein, and 0.1% of Rose Bengal) wasadded, and thereby a photoconductive substance, that is, a sensitizerdispersed solution, was produced. Next, 80 gms. of the aforesaid bindersolution was added to said dispersed solution and, through thoroughagitation, a photoconductive-layer forming solution was produced.Subsequently, by application of this solution and also following thesame processes for forming a photoconductive layer as employed inExample 1, an electrophotographic copying material was Obtained.

Meanwhile, for the purpose of comparing the efficiency and performanceof the copying material obtained in the present invention, anotherbinder was prepared by emulsifying the aforesaid resin by means of sucha conventional surface active agent that will scarcely be volatilizedeven by drying, and by application of said binder, and through the sameprocesses as in the present invention, an electrophotographic copyingmaterial was also prepared to serve for the test comparison.

When both of the aforesaid copying materials were impressed with anelectric charge through a conventional process, exposed, and thendeveloped by either the wetprocess or the dry-process, the copyingmaterial which was produced in accordance with the present inventionformed a clear image, whether developed by the Wetprocess or thedry-process, while the other one employed for comparison could hardlyform any image regardless of the process of development.

Example 19 In this case, 15 gms. of Beckozole 1341 was added to 70 gms.f Silicone Resin KR-2l1, and the mixture thus obtained was agitated by ahomomixer while another solution, which had been prepared by dissolving5 .gms. of morpholine in 100 gms. of water, was added steadily, andthereby a binder solution comprising an emulsion of said Silicone ResinKR-211 was produced. Then, 80 gms. of the thus obtained binder solutionwas added to a photoconductive substance, that is, a sensitizerdispersed solution having the same composition as that of Example 18,and was blended thoroughly by agitation, thereby producing aphotoconductive layer forming solution. Subsequently, said solution wasused in the same way as in Example 18, and an electrophotographiccopying material was obtained thereby. The resultant coping material,when employed for the photographic reproduction by following the sameprocesses as in Example 18, produced quite a clear copied image.

Example 20 In this case, gms. of 70%-mineral turpentine solution ofSuper Beckozole 1351 (a pure alkyd resin whose acid value isapproximately 20, manufactured by Dai Nippon Ink and Chemicals Inc.) wasadded to 70 gms. of a xylene solution of Silicone Resin (KR-211) whichis the same as that of Example 19, and the mixture thus obtained wasagitated by a homomixer while another solution, which had been preparedby dissolving 3 gms. of triethylamine in 100 gms. of water, was addedsteadily, and thereby a binder solution comprising an emulsion of saidSilicone Resin KR-211 was produced. Subsequently, 80 gms. of the thusobtained binder solution was processed for application in the same wayas in Example 18, and an electrophotographic copying material wasproduced thereby.

Example 21 In this case, except for substitution of gms. of 50%-toluenesolution of Aron S-lOOl (trade name of product of Toa Gosei Kagaku KogyoKabushiki Kaisha, whose acid value is approximately 12) which is acopolymer resin whose principal component is an acrylic ester, for thesolution of a pure alkyd resin employed in the foregoing Example 20, thesame components and processes of treatment as in Example were applied inobtaining an electrophotographic copying material. The efiiciency andperformance of the resultant copying material were equivalent to that ofExample 20.

Example 22 In this case, except for substitution of 15 gms. of solutionof a styrenated alkyd resin (i.e. the same as employed in Example 18)for the solution of a pure alkyd resin employed in Example 20, the samecomponents and processes of treatment were applied in obtaining an elec-14 trophotographic copying material. The efficiency and performance ofthe resultant copying material were equivalent to that of Example 20.

Example 23 In this case, except for the substitution of 10 gms.

of 50%-xylene and butanol solution of Lustrazol A-401 (a manufacture ofDai Nippon Ink and Chemicals Inc., whose acid value is approximately 5),which is a copolymer resin whose principal component is an acrylicester, for the solution of pure alkyd resin employed in the aforesaidExample 20, the same components and processes of treatment were appliedin obtaining an electrophotographic copying material. The efficiency andperformance of the resultant copying material were equivalent to that ofExample 20.

Example 24 In this case, 0.5 gr. of manganese naphthenate (a hardener)was added to 100 gms. of a mineral turpentine solution of a styrenatedalkyd resin (i.e. the same as employed in Example 18), and this mixturewas agitated b a homomixer while another solution, which had beenprepared by dissolving 3 gms. of triethylamine in 100 gms. of water, wasadded steadily, and thereby a binder solution comprising an emulsion ofsaid resin was produced. On the other hand, 0.25 gr. of manganesenaphthenate and 0.25 gr. of cobalt naphthenate were added to 100 gms.(50 gms. solid) of a mineral turpentine solution of rosin-modified alkydresin (manufactured by Japan Reichhold Chemicals Inc.), and this mixturewas agitated by a homomixer while another solution, which had beenprepared by dissolving 2 gms. of triethylamine and 1 gr. oftrimethylamine in 100 gms. of water, was added thereto, and was therebyemulsified. Subsequently, 100 gms. each of the binder solutions thusemulsified was respectively added to a photoconductive substance, thatis, a sensitizer dispersed solution having the same composition as thatof the aforesaid Example 18, and blended thoroughly by agitation,thereby producing two types of photoconductive layer forming solutions.Then, said solutions were respectively treated in the same way as inExample 18, and electrophotographic copying materials were obtainedthereby. The resultant copying materials when employed for copying, haveproved equivalent to that of Example 18 in their efiiciency andperformance.

Example 25 In this case, 600 gms. of toluene, 270 gms. of styrene, 200gms. of butyl methacrylate, 60 gms. of -hydroxypropylmethacrylate, 20gms. of itaconic acid, and 12 gms. of azobisisobutyronitrile were puttogether in a three neck flask, and upon replacing the air within saidflask by nitrogen, said mixture was polymerized over a period of 5 hoursby heating at 100 C., and thereby a copolymerized resinous binder(hereinafter referred to as copolymer A) was obtained.

Next, 3 gms. of naphthenic acid was added to 100 gms. of said copolymerA, and this mixture was agitated by a homomixer while 100 gms. of3%-aqueous solution of triethylamine was added steadily, and thereby abinder solution comprising an emulsion of said copolymer A was produced.

Then, 100 gms. of photoconductive zinc oxide, 100 gms. of water, and 1gr. of tartaric acid were added to gms. of said emulsified binder, andthe mixture thus obtained was further agitated by a homomixer for 10min. Subsequently, 3 cc of a sensitizer solution (a methanol solutioncomprising 1% of Bromophenol Blue and 0.5% of Rose Bengal) was added tothe resultant solution, and a photosensitive-layer forming solution wasproduced thereby. The photosensitive-layer forming solution thusproduced was applied for coating the surface of an art paper, whose backhad been processed for conductivity, to such an extent that theremainder of the applied sensitizer on said surface subsequent to thedrying process was 30 gms./m1 Then, the thus coated support was dried at120 C. for 10 min. and thereafter left in a dark place (temp. C., RH65%) for modulation of the humidity for 24 hours, and thereby anelectrophotographic copying material was obtained.

On the other hand, for the sake of comparison, another copying materialwas prepared by means of employing a copolymer which was composed bymerely omitting the 'y-hydroxypropylmethacrylate from the components ofthe aforesaid polymer A, while processing it in the same way as wasemployed above. (Said copying material thus obtained for the sake ofcomparison is hereinafter referred to as compared material a.) Also, forthe same purpose of comparison, one more sample of copying material wasalso prepared by means of employing an emulsified binder obtained byemulsifying the aforesaid copolymer A by use of sodiumalkylbenzenesulfonate, while processing it in the same way as wasemployed in the present invention. (Said copying material thus obtainedfor the sake of compa)rison is hereinafter referred to as comparedmaterial b.

Subsequently, evaluation of each of the foregoing copying materials wasconducted with regard to their electrostatic characteristics as shownbelow:

The results of evaluations conducted on the respective characteristicsof the aforesaid materials Were as shown in the following Table 1.

TABLE 1 Electric charge- Dark Sensitivability decay ity Copying materialVs (V /p) (percent) (lux/sec.)

Material of present invention 40 10 320 Compared material .9 35 30 360Compared material b 5 100 Furthermore, as a result of putting therespective copying materials into practical use for the formation ofcopies, it was found that the material of the present invention wasquite superior to the compared material a while the compared material bwas conspicuously inferior to the compared material a in terms of theconcentration of image and clearness of the produced copy.

Example 26 In this case, except for containing the same amount offi-hydroxyethylmethacrylate in lieu of 'y-hydroxypropylmethacrylate, acopolymer having the same composition as the copolymer A in theforegoing Example was prepared. This copolymer is hereinafter referredto as copolymer B. Then, said copolymer b was processed in the same wayas in Example 25, and thereby an electrophotographic copying materialwas obtained.

On the other hand, for the sake of comparison of efficiency, anothercopolymer comprising the components of the aforesaid copolymer B,excluding the fl-hydroxyethylmethacrylate, was prepared through the sameprocesses as employed in the present invention, and thereby a copyingmaterial to serve for comparison was produced.

As a result of comparison of the efficiency and performance in terms ofthe concentration of image and clearness of produced copy as well aselectrostatic characteristics of of these copying materials, it wasfound that the material of the present invention was far superior tosaid comparison material.

Example 27 In this case, 'y-hydroxypropylmethacrylate of the copolymer Ain Example 25 was replaced with the same weight ofp-hydroxyethylacrylate, while the composition ratio of other monomerswas left the same. Into 100 gms. of the copolymer thus prepared(hereinafter referred to as copolymer C) was added 3 gms. of phthalicacid, and this mixture was thoroughly agitated by a homomixer while 3%aqueous solution of trimethylamine was added steadily, to emulsify andproduce a binder thereby.

Subsequently, 100 gms. of photoconductive zinc oxide, 100 gms. of water,and 3 cc. of sensitizing dye (the same composition as in Example 1) wereadded to gms. of the thus emulsified binder solution, and agitated by ahomomixer for 10 min. Then, by employing the processes and a support thesame as that used in Example 25, an electrophotographic copying materialwas obtained.

On the other hand, another copolymer was produced by excludingB-hydroxyethylacrylate from said copolymer C while leaving thecomposition ratio of the other monomers the same, and following the samesteps as in the present invention, so as to provide a copying materialfor the purpose of comparison. Then, evlauation of the electrostaticcharacteristics of each of the aforesaid copying materials was conductedby the same method as in Example 25. The values thus determined areshown in the following Table 2.

In case of the copying material in the present invention, it isunderstood that, either in the course of the drying or while in thestate of being heated subsequent to the drying of the sensitive solutionapplied to the surface of a support, trimethylamine contained in saidsolution was volatilized, and a carboxylic acid such as itaconic acid orphthalic acid and the -OH radical of fl-hydroxyethylacrylate caused abridging-reaction, and accordingly, the copying material of the persentinvention proved satisfactory in respect of its electrostaticcharacteristics as well as its copoying performance as compared withthose materials employed for comparison.

Example 28 In this case, a composition of monomers comprising 500 gms.of toluene, 200 gms. of styrene, 150 gms. of butyl methacrylate, 50 gms.of ethyl acrylate, 58 gms. of acrylonitrile, 40 gms. ofglycidylmethacrylate, 2 gms. of acrylic acid, and 8 gms. of benzoylperoxide was slowly agitated within a three neck flask, in which air hadbeen replaced by nitrogen, while being heated at C. for a 6-hourpolymerization. Subsequently, the thus polymerized product was cooled,and a 50% solid copolymer was obtained thereby. (This material ishereinafter referred to as copolymer D.)

Next, 10 gms. of Styrezol 4440 and 3 gms. of phthalic anhydride wereadded to gms. of said copolymer D. The mixture thus obtained wasagitated by a homomixer while 100 gms. of 3%-aqueous solution ofisopropylamine [(CH CHNH was added steadily, and was emulsified.

Then, 100 gms. of zinc oxide powder, 100 gms. of Water, and 4 cc. ofsensitizing dye (is. a methanol solution comprising 0.5% of BromophenolBlue and 0.5 of

Rose Bengal) were added to 80 gms. of said emulsion. This mixture wasintensely agitated for blending for 10 min., and a photosensitive-layerforming solution was thus obtained.

Meanwhile, the employment of an aqueous solution of a polymer comprisingan inorganic salt such as sodium chloride or lithium chloride, the backof an art paper was processed for electric conductivity. The surface ofthe thus processed art paper was then coated with the aforesaidphotoconductive-layer forming solution to such an extent that theresidue of coating substance (i.e. sensitizer) after drying will be 30gms./11 The art paper thus coated was dried at 120 C. for 10 min. andthereafter left hung in a dark place (temp. 20 0, RH 65%) for 12 hoursfor modulation of humidity, and hereby an electrophotographic copyingmaterial was obtained.

On the other hand, for the purpose of comparison, another copyingmaterial was produced by employing a co polymer which was composed bymerely omitting glycidylmethacrylate from the components of theaforesaid copolymer D, while processing it in the same way as in thepresent invention.

A subsequent careful comparison in respect of the electrostaticcharacteristics as well as the actual electrophotographic copyingperformance revealed that the electric charge of the copying material inthe present invention is higher than that of the aforesaid materialprovided for comparison, and that the degree of dark decay of the formeris lower than that of the latter. It has also been confirmed that theformer is conspicuously superior to the latter in the image formabilityand the concentration of image. Moreover, it was observed that such acopying material as produced by employing an emulsion prepared byemulsifying the aforesaid copolymer D by means of a surface active agentsuch as nonionic, cationic, anionic, or amphoteric ion surface activeagent was either utterly ineffective in image-formation or could produceonly an unclear image (whose concentration was in the range of 0.2-0.4).

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. The method of preparing an electrophotographic copying materialcomprising an electroconductive support having a photoconductive filmlayer on one surface thereof, the said material being capable ofassuming and retaining an image-forming electrostatic charge, whichmethod comprises forming an aqueous emulsion of a resinous binder andcontaining dispersed therein a finely divided photoconductive material,by emulsifying a resinous binder of a copolymer consisting of at leastone member selected from the vinyl monomer group consisting of glycidylacrylate, glycidyl methacrylate, hydroxyethyl methacrylate, hydroxyethylacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate,5-hydroxypentylvinyl ether (CHFCHOCHQCHZCHZCHZCHZOH) with at least onemember selected from the monomer group consisting of styrene, alkylacrylate, alkyl methacrylate, acrylonitrile, vinyl chloride, vinylidenechloride, vinyl acetate, acrylic acid, methacrylic acid, crotonic acid,itaconic acid, maleic acid and fumaric acid, in the presence of anacidic substance and in an aqueous solution of a volatile base as soleemulsifying agent, said acidic substance being selected from the groupconsisting of natural resins containing resin acid and having anelectric resistance of at least 9-cm., synthetic resins containing acarboxyl radical and having an electric resistance of at least 10 0-cm.,alicyclic compounds having a carboxyl radical, aliphatic carboxylicacids, aromatic carboxylic acids and acid anhydrides of said carboxylicacids; applying a film of said emulsion onto said conductive support anddrying said film for a time sufficient to evaporate substantially all ofsaid volatile base.

2. The method of claim 1 in which the volatile base is a member selectedfrom the group consisting of ammonia, a lower aliphatic amine, anaromatic amine, morpholine and piperidine.

3. The method of claim 1 wherein the emulsifying step comprises mixingan organic solvent solution of said resinous binder and said acidicsubstance and an aqueous solution of said volatile base.

4. An electrophotographic copying material comprising anelectro-conductive support and having applied thereon a photoconductivefilm comprising a resinous binder having dispersed therein aphotoconductive substance selected from the group consisting of zincoxide, titanium oxide, cadmium sulfide and zinc selenide, said resinousbinder consisting of a copolymer of at least one member selected fromthe vinyl monomer group consisting of glycidyl acrylate, glycidylmethacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate,hydroxypropyl methacrylate, hydroxypropyl acrylate, S-hydroxypentylvinylether (CH CHOCH CH CH CH CH OH) with at least one member selected fomthe monomer group consisting of styrene, alkyl acrylate, alkylmethacrylate, acrylonitrile, vinyl chloride, vinylidene chloride, vinylacetate, acrylic acid, methacrylic acid, crotonic acid, itaconic acid,maleic acid and fumaric acid, and being one which is water-emulsifiablein the presence of an acidic substance and a volatile base to form anemulsion stable upon mixing with said photoconductive substance, saidfilm having dispersed therein an acidic substance selected from thegroup consisting of natural resins containing resin acid and having anelectric resistance of at least IO Q-cm, synthetic resins containing acarboxyl radical and having an electric resistance of at least 10 Q-cm,alicyclic compounds having a carboxyl radical, aliphatic carboxylicacids, aromatic carboxylic acids and acid anhydrides of said carboxylicacids, said film having been dried for a time sufiicient to evaporatesubstantially all of said volatile base.

5. The article of claim 4 which also contains a small amount notexceeding 0.5% per total weight of said photoconductive film of avolatile base.

6. The article of claim 4 wherein said photoconductive film contains avolatile base selected from the group consisting of ammonia,methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine,triethylamine, propylamine, butylamine, hexylamine, ethylenediamine,arylamine, morpholine, piperidine and hydrazine, said volatile basebeing present in said film within a range not exceeding 0.5% per totalweight of said photoconductive film.

References Cited UNITED STATES PATENTS Re. 25,444 9/1963 Kucera 96--12,997,387 8/1961 Tanenbaum 96-4 3,159,483 1/1964 Behmenhey et al. 96--13,160,503 12/1964 Cady 961 3,245,786 4/ 1966 Cassiens 96-1 3,248,2174/1966 Shulman 96-1 3,261,709 7/1966 Shulman 11734 3,307,942 3/1967 Cole96-1.8 3,409,575 11/1968 Cole 260-27 3,345,162 10/1967 McFarline 961.83,489,559 1/1970 Clark 96--1.5

OTHER REFERENCES Fundamental Principles of Polymerization by DAlelio,Wiley & Sons, New York, N.Y., 1952, p. 202.

JOHN C. COOPER III, Primary Examiner US. Cl. X.R.

